/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.messaging.handler.invocation;

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.messaging.Message;

/**
 * Resolves method parameters by delegating to a list of registered
 * {@link HandlerMethodArgumentResolver}. Previously resolved method parameters are cached
 * for faster lookups.
 *
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 4.0
 */
public class HandlerMethodArgumentResolverComposite implements HandlerMethodArgumentResolver {

    private final List<HandlerMethodArgumentResolver> argumentResolvers = new LinkedList<>();

    private final Map<MethodParameter, HandlerMethodArgumentResolver> argumentResolverCache =
            new ConcurrentHashMap<>(256);


    /**
     * Add the given {@link HandlerMethodArgumentResolver}.
     */
    public HandlerMethodArgumentResolverComposite addResolver(HandlerMethodArgumentResolver argumentResolver) {
        this.argumentResolvers.add(argumentResolver);
        return this;
    }

    /**
     * Add the given {@link HandlerMethodArgumentResolver}s.
     *
     * @since 4.3
     */
    public HandlerMethodArgumentResolverComposite addResolvers(@Nullable HandlerMethodArgumentResolver... resolvers) {
        if (resolvers != null) {
            for (HandlerMethodArgumentResolver resolver : resolvers) {
                this.argumentResolvers.add(resolver);
            }
        }
        return this;
    }

    /**
     * Add the given {@link HandlerMethodArgumentResolver}s.
     */
    public HandlerMethodArgumentResolverComposite addResolvers(
            @Nullable List<? extends HandlerMethodArgumentResolver> argumentResolvers) {

        if (argumentResolvers != null) {
            for (HandlerMethodArgumentResolver resolver : argumentResolvers) {
                this.argumentResolvers.add(resolver);
            }
        }
        return this;
    }

    /**
     * Return a read-only list with the contained resolvers, or an empty list.
     */
    public List<HandlerMethodArgumentResolver> getResolvers() {
        return Collections.unmodifiableList(this.argumentResolvers);
    }

    /**
     * Clear the list of configured resolvers.
     */
    public void clear() {
        this.argumentResolvers.clear();
    }


    /**
     * Whether the given {@linkplain MethodParameter method parameter} is supported by any registered
     * {@link HandlerMethodArgumentResolver}.
     */
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return getArgumentResolver(parameter) != null;
    }

    /**
     * Iterate over registered {@link HandlerMethodArgumentResolver}s and invoke the one that supports it.
     *
     * @throws IllegalStateException if no suitable {@link HandlerMethodArgumentResolver} is found.
     */
    @Override
    @Nullable
    public Object resolveArgument(MethodParameter parameter, Message<?> message) throws Exception {
        HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
        if (resolver == null) {
            throw new IllegalStateException("Unknown parameter type [" + parameter.getParameterType().getName() + "]");
        }
        return resolver.resolveArgument(parameter, message);
    }

    /**
     * Find a registered {@link HandlerMethodArgumentResolver} that supports the given method parameter.
     */
    @Nullable
    private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
        HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
        if (result == null) {
            for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {
                if (resolver.supportsParameter(parameter)) {
                    result = resolver;
                    this.argumentResolverCache.put(parameter, result);
                    break;
                }
            }
        }
        return result;
    }

}
